David Johnston, who is the British queen's representative in Canada where she is head of state, joined the likes of former U.S. first lady Michelle Obama in breaching unspoken rules of behaviour when meeting the monarch.
He took Elizabeth by the elbow as she descended red-carpeted stairs outside London's Canada House following an event to celebrate 150 years of Canadian independence.
"I´m certainly conscious of the protocol. I was just anxious to be sure that there was no stumbling on the steps," Mr Johnson told Canadian broadcaster CBC news.
"It's a little bit awkward, that descent from Canada House to Trafalgar Square, and there was carpet that was a little slippy, and so I thought perhaps it was appropriate to breach protocol just to be sure that there was no stumble."
The royal family's official website states that "there are no obligatory codes of behaviour when meeting the Queen or a member of the Royal Family" but suggests people might wish to observe "traditional forms".
"For men this is a neck bow (from the head only) whilst women do a small curtsy. Other people prefer simply to shake hands in the usual way," the website says.
However, the protocol is that no one should touch the monarch and other foreign political figures have come under fire for doing so.
Former Australian Prime Minister Paul Keating was dubbed the "Lizard of Oz" by the British press after he appeared to put his arm around the queen's shoulders in 1992.
In 2004, ex-French President Jacques Chirac was warned to keep his "Hands Off!" by Britain's Daily Mail newspaper after he appeared to touch the monarch when she visited a Parisian market.
However, the queen seemed happy for Barack Obama's wife to break the protocol when she visited Buckingham Palace with the former U.S. president in 2012 when they both put arms around each other in what was described as a friendly hug.